I feel you.

I've got a 13 year old daughter with DS. We don't have 6 hours of screaming but she has definitely thrown her share of hissy fits. My personal favorite was driving into my son's snooty private boy's school while she was sitting in the back without a shirt on (She was 12 at the time).

Or the time she decided to sit down in the middle of a busy street while we were trying to cross it and we ended up dragging her across the road skinning her feet and almost getting hit by a truck.

Usually she is happy and has tons of personality but it really does make things harder at times.

I should probably add my that my usual comment when anyone asks is that having a kid with DS sucks but not as badly as a lot of other disabilities.